Tropical Cyclone Track Sensitivity in Deformation Steering Flow
Tropical Cyclone Track Sensitivity in Deformation Steering Flow
复制标题
DOI：
10.1175/mwr-d-18-0153.1
复制
发表时间：
2018-09
影响因子：
3.2
通讯作者：
R. Torn;Travis J. Elless;P. Papin;C. Davis
中科院分区：
文献类型：
--
作者：
R. Torn;Travis J. Elless;P. Papin;C. Davis
以往的研究表明，变形导向气流中的热带气旋(TC)可能与较大的位置误差和不确定性有关。本研究的目的是利用欧洲中期天气预报中心(ECMWF)集成预报的基于集合的敏感性技术，评估三个TC在形变风场[Debby(2012)，Joaquin(2015)，LionRock(2016)]内位置预报的敏感性。在这三种情况下，位置预报都对0-h热带气旋位置500公里范围内的导向风的不确定性很敏感。随后，由于系综扰动转向气流，热带气旋移动到收缩轴的两侧。当热带气旋离开鞍点时，集合成员随后经历不同的集合平均导向风，这使得热带气旋沿着扩张轴远离集合平均热带气旋位置。相比之下，位置预报对距初始热带气旋位置500公里以上的导向风的敏感度似乎较低，即使热带气旋可能会在稍后的预报中与这些特征相互作用。此外，在稍后时间启动的预报的特点是，一旦TC将在收缩轴的哪一侧移动变得清晰，位置误差和不确定性就会显著降低。这些结果表明，变形转向气流中的TC可能本质上是不可预测的，并可能受益于在生命周期早期对近风暴转向气流和TC结构进行密集采样。
Previous studies have suggested that tropical cyclones (TCs) in deformation steering flows can be associated with large position errors and uncertainty. The goal of this study is to evaluate the sensitivity of position forecasts for three TCs within deformation wind fields [Debby (2012), Joaquin (2015), and Lionrock (2016)] using the ensemble-based sensitivity technique applied to European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecasts. In all three cases, the position forecasts are sensitive to uncertainty in the steering wind within 500 km of the 0-h TC position. Subsequently, the TC moves onto either side of the axis of contraction due to the ensemble perturbation steering flow. As a TC moves away from the saddle point, the ensemble members subsequently experience different ensemble-mean steering winds, which act to move the TC away from the ensemble-mean TC position along the axis of dilatation. By contrast, the position forecasts appear to exhibit less sensitivity to the steering wind more than 500 km from the initial TC position, even though the TC may interact with these features later in the forecast. Furthermore, forecasts initialized at later times are characterized by significantly lower position errors and uncertainty once it becomes clear on which side of the axis of contraction the TC will move. These results suggest that TCs in deformation steering flow could be inherently unpredictable and may benefit from densely sampling the near-storm steering flow and TC structure early in their lifetimes.